The present invention generally relates to organic electroluminescence. More particularly, the present invention pertains to an organometallic complex molecule and an organic electroluminescent (hereinafter referred to as xe2x80x9corganic ELxe2x80x9d) device using the organometallic complex molecule.
Organic electroluminescence is one of the instances, in which electric current is directly converted into visible light by internal processes of organic fluorescent or light-emitting molecules. In recent years, great attention has been given to the improvement of organic EL technology since it can be used in a new type of flat panel display, which can replace the liquid crystal display (LCD) technology. Individual colors of red, green is or blue can be emitted, or they can be combined to create fill color image display. This technology is advantageous over LCD technology in its low power consumption, faster response time, higher brightness level, unlimited viewing angle and tinner design.
A basic construction of an organic EL device includes two opposing electrodes, i.e., a cathode and an anode, and an intervening layer containing an organic light-emitting or fluorescent material. When applying an electric voltage between the electrodes, electrons and holes are injected from the cathode and the anode, respectively, into the intervening layer and recombined therein Recombined pairs of electrons and holes, namely excitons, move around carrying the energy generated by the recombination and transfer the energy to the organic fluorescent molecules. The transferred energy excites valence electrons of the organic fluorescent molecules and generate photons when the electrons return to their ground state.
In order to improve energy efficiency, multiple-layered organic EL devices have been suggested. Generally, multiple-layered organic EL devices have one or more of hole-injecting layer, hole-transporting layer, light-emitting layer, electron-transporting layer, and electron-injecting layer. The carrier (electron or hole) injecting layer or carrier transporting layer may work as a light emitting layer as well when organic fluorescent materials arc doped therein. Organic EL devices having multiple layers are expensive to manufacture due to the significant accompanying processing. Thus, it is desirable that one layer of the organic EL device has multiple functions: e.g., one for electron-injection/transportation as well as light-emission.
In order to improve luminescence efficiency of a light-emitting layer, another light-emitting material having a higher quantum yield is doped in the light-emitting layer. Excitons are known to have a tendency to transfer their energy to a material having a smaller band gap among materials near the recombination location. Accordingly, a dopant is selected from materials having a high quantum yield and a smaller band gap (larger wavelength) than the host material; otherwise, the excitons"" energy will transferred the host material having a lower quantum yield, accordingly generating weak or no emission.
Tris (8-hydroxyquinoline) aluminum complex (Alq3) is known as a material having light-emitting and electron-injection/transportation properties. Alq3 has a band gap for green light emission. Accordingly, blue light-emitting materials are not suitable for doping in an Alq3 layer Although DPVBi and B-Alq emitting blue light can be used as an electron-transporting material, these materials require a high driving voltage when directly contacting the cathode because of their high reduction potentials. In order to use these materials in a light-emitting layer functioning as the electron-transporting as well, a separate electron-injection layer is needed.
One aspect of the present invention provides an organometallic complex for use in organic EL devices. The complex compounds have a structure satisfying the following Chemical Formula (1): 
In the Chemical Formula (1), xe2x80x9cXxe2x80x9d is, with or without a functional group bonded thereto, one selected from the group consisting of carbon, oxygen, sulfur, selenium, and nitrogen with an alkyl or aromatic functional group. xe2x80x9cZxe2x80x9d is, with or without a functional group bonded thereto, one selected from the group consisting of carbon, oxygen, sulfur, selenium and nitrogen with an alkyl or aromatic functional group. xe2x80x9cMxe2x80x9d is a metal and preferably is a monovalent divalent or trivalent metal. xe2x80x9cnxe2x80x9d is a positive integer depending upon the oxidation state of the metal xe2x80x9cMxe2x80x9d. xe2x80x9cAxe2x80x9d and xe2x80x9cBxe2x80x9d are functional groups comprising one or more ring structures. All the implicit hydrogens of Chemical Formula (1) can be substituted with any functional groups, including alky, aryl, halogen, amino, etc.
Another aspect of the present invention provides a light-emitting composition, which comprises an organometallic complex having a structure satisfying Chemical Formula (1).
Another aspect of the present invention provides an electron-transporting composition, which comprises an organometallic complex having a structure satisfying Chemical Formula (1).
Another aspect of the present invention provides an organic EL device, which comprises a a first electrode, a second electrode opposing the first electrode, and a first layer located between the first electrode and the second electrode. The first layer contains an organometallic complex having a structure satisfying Chemical Formula (1).
Still another aspect of the present invention provides an electronic device, which comprises a organic EL device display, making use of an organometallic complex.
Still another aspect of the present invention provides a method of generating visible light from an electronic device. The method comprises injecting electrons and holes from two opposing electrodes into at least one layer located between the two electrodes by applying electric power to the two electrodes. The at least one layer contains an organometallic complex satisfying Chemical Formula (1).
Still another aspect of the present invention provides a method of manufacturing an organic EL device. The method comprises providing a substrate, forming a first conductive layer, forming at least one layer; and forming a second conductive layer. The at least one layer contains an organometallic complex of Chemical Formula (1).
Still further aspect of the present invention provides an electroluminescent (EL) device. The device comprises a cathode, an anode, and a layer of material therebetween. The layer of material comprises a compound having the formula M(O), wherein xe2x80x9cMxe2x80x9d is a metal; xe2x80x9cnxe2x80x9d is a positive integer depending upon the oxidation state of the metal xe2x80x9cMxe2x80x9d; and xe2x80x9cAxe2x80x9d is an organic moeity comprising a plurality of bonded ring structures. The layer of material directly contacts the cathode.